This invention relates generally to windmills and more specifically to a mechanism providing for selective positioning of a wind responsive surface on a windmill.
A preliminary novelty search conducted in connection with the present invention developed the following U.S. patents.
U.S. Pat. Nos. 3,743,848, 3,793,530, 3,902,072, 3,995,170, 4,031,405, 4,066,911, 4,184,084, 4,329,593, 4,346,506.
These patents relate to various windmills in which wind responsive surfaces are caused to assume various positions in relation to the wind as the windmill is rotated by the wind. In a vertical axis windmill, one objective is to increase efficiency of operation so that over the half revolution which has a leeward component of motion, maximum wind utilization is obtained, while over the half revolution which has a windward component of motion, resistance is minimized. Increased efficiency is especially important at relatively low wind velocities.
One example of this objective is demonstrated in U.S. Pat. No. 4,184,084 in which the wind responsive surfaces are rigid vanes. As a vane travels along the semi-circular segment of motion which has a windward component, it aligns with the wind so as to continuously present minimum wind resistance over that half revolution of travel. As a vane travels over the semi-circular segment of motion which has a leeward component. It is constrained against rotation so that it always captures at least some of the wind.
U.S. Pat. No. 3,995,170 discloses a windmill which is allegedly able to take advantage of the wind over slightly more than 180.degree. of one complete revolution (360.degree.).
The present invention relates to an improved windmill mechanism for adjusting the position of a wind responsive surface in relation to wind to obtain greater efficiency. It employs large sails and the sailing principle. When travelling on a circular path, a sail can take advantage of the wind over more than 300.degree. of a revolution. This construction and arrangement make the windmill very efficient especially in low wind speeds. As noted above, improved efficiency is important, particularly for low wind speed operation.
In addition to the improved efficiency of operation which is obtained with the present invention, a further improvement is obtained by virtue of the construction and arrangement of the wind responsive surfaces and their supports. Specifically the wind responsive surfaces and their supports, in their preferred form, are constructed and arranged so as to automatically compensate for higher wind speeds by automatic feathering. This renders them less prone to damage in response to sudden wind gusts and high wind speeds, and it also means that their mass can be kept lower than might otherwise be the case. By minimizing mass, improved control is obtained. This further increases the efficiency of operation.